Boiler system with a support construction

Abstract

A boiler system includes a support construction and a furnace supported to the support construction at a vertically middle section of the furnace, the furnace being enclosed by water tube walls having two side walls and two end walls, a roof and a bottom, the side walls having a total height (H) from the bottom to the roof. Each of the two side walls has a vertical upper portion that extends from the roof to a level of thirty to seventy percent of the height (H), a lower portion that extends from the bottom to a level of thirty to seventy percent of the height (H) and has a vertical upper portion, and an in downward direction outwards bent intermediate portion at a level between the upper portion of the side wall and the vertical upper portion of the lower portion of the side wall. The support construction includes horizontal wall supporting beams that are arranged parallel to the side walls at a level below the roof of the furnace and directly above the vertical upper portions of the lower portions of the two side walls, and the furnace is supported to the support construction by having the intermediate portions of the side walls connected to adjacent horizontal wall supporting beams so as to balance vertical loads of the furnace.

Claims

1. A boiler system comprising: a support construction; and a furnace supported to the support construction at a vertically middle section of the furnace, the furnace being enclosed by water tube walls comprising two side walls and two end walls, a roof, and a bottom, the side walls having a total height H from the bottom to the roof, wherein each of the two side walls comprises a vertical upper portion that extends from the roof to a level of thirty to seventy percent of the height H, a lower portion that extends from the bottom to a level of thirty to seventy percent of the height H and has a vertical upper portion of the lower portion of the side wall, and an in downward direction, outwards bent intermediate portion, at a level between the vertical upper portion of the side wall and the vertical upper portion of the lower portion of the side wall, wherein (i) the support construction comprises horizontal wall supporting beams at a level below the roof of the furnace, (ii) the horizontal wall supporting beams are arranged parallel to the two side walls and directly above the vertical upper portions of the lower portions of the two side walls, and (iii) the furnace is supported to the support construction by having the intermediate portions of the two side walls connected to the horizontal wall supporting beams so as to balance vertical loads of the furnace.

2. The boiler system according to claim 1, wherein the horizontal wall supporting beams are arranged at a level of thirty to seventy percent of the height H from the bottom of the furnace.

3. The boiler system according to claim 1, wherein the support construction comprises a first portion having multiple vertical columns supported to foundations of the boiler system.

4. The boiler system according to claim 3, wherein the support construction further comprises multiple fixed horizontal beams firmly supported to the vertical columns and a second portion that is movably connected to the first portion and comprises the horizontal wall supporting beams.

5. The boiler system according to claim 4, wherein each of the horizontal wall supporting beams is movably supported to at least two of the fixed horizontal beams.

6. The boiler system according to claim 5, wherein the at least two fixed horizontal beams are arranged parallel to the end walls of the furnace.

7. The boiler system according to claim 6, wherein the at least two fixed horizontal beams comprise at least two of one or more horizontal beams arranged outside an end wall of the furnace and one or more cantilever beams protruding towards a central portion of a side wall of the furnace.

8. The boiler system according to claim 7, wherein each of the horizontal wall supporting beams is supported on sliding surfaces arranged on the at least two fixed horizontal beams.

9. The boiler system according to claim 7, wherein each of the horizontal wall supporting beams is supported to be hanging by at least two main hanger rods from the at least two fixed horizontal beams.

10. The boiler system according to claim 1, wherein vertical loads of the furnace are balanced solely by the horizontal wall supporting beams.

11. The boiler system according to claim 1, wherein the horizontal wall supporting beams are arranged inside a common thermal insulation with the furnace.

12. The boiler system according to claim 1, wherein each of the intermediate portions of the side walls is supported to an adjacent horizontal wall supporting beam by a plurality of short hanger rods that are aligned with the vertical upper portion of the lower portion of the respective side wall.

13. The boiler system according to claim 12, wherein each of the short hanger rods is by a support lug attached to an outer edge of the in downward direction outwards bent intermediate portion of the respective side wall.

14. The boiler system according to claim 12, wherein the distance between adjacent hanger rods is N times the distance between adjacent vertical water tubes of the water tube wall of the respective side wall.

15. The boiler system according to claim 14, wherein N is an integer of at most three.

16. The boiler system according to claim 14, wherein N is at most two.

17. The boiler system according to claim 14, wherein N is one.

18. The boiler system according to claim 1, wherein the furnace is the furnace of a fluidized bed boiler.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a side view of a boiler system according to a preferred embodiment of the present invention.

(2) FIG. 2 schematically illustrates a horizontal top view of the boiler system of FIG. 1.

(3) FIG. 3 schematically illustrates a detail of the suspension of a furnace according to an embodiment of the present invention.

(4) FIG. 4 schematically illustrates a side view of a boiler system according to another preferred embodiment of the present invention.

(5) FIG. 5 schematically illustrates a side view of a boiler system according to a third preferred embodiment of the present invention.

(6) FIG. 6 schematically illustrates another side view of the boiler system of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 schematically illustrates a side view of a fluidized bed boiler system 10, in accordance with an embodiment of the present invention. The fluidized bed boiler system 10 comprises a furnace 12 having a bottom 14 and a roof 16 at a height H from the bottom, two side walls 18 and two end walls 20, only one of which is seen in FIG. 1. The side walls 18 and end walls 20 are of a conventional type, consisting of vertical water tubes 22 connected together by fins. The boiler can be either a drum boiler or a once-through boiler. The furnace 12 also comprises other conventional equipment, such as a flue gas duct 24 and a device for feeding fuel 26 and primary air 28 to the furnace. Because such equipment is not relevant for understanding the present invention, they are not described here in detail.

(8) The side walls 18 comprise a vertical upper portion 30 and a lower portion 32 with an inwards slanted bottom portion 34 and a vertical upper portion 36. Between the vertical upper portion 30 and the vertical upper portion 36 of the lower portion 32 of the side wall 18, there is an in downward direction outwards bent intermediate portion 38.

(9) In the case of a fluidized bed boiler system 10 having a rectangular furnace 12 enclosed by two longer walls and two shorter walls, the shorter walls, which are generally vertical, are usually considered to be the end walls. Thus, the supporting of the furnace 12 according to the present invention is made on the longer walls, which are considered to be the side walls. A cross section of such a furnace is seen in FIG. 2. On the other hand, the furnace 12 of a circulating fluidized bed boiler with only one particle separator usually has an at least nearly square cross section. In such a case, any two of the enclosing walls can be considered to be the side walls as in the present description, i.e., the supporting of the furnace according to the present invention can be made on any two mutually opposing walls of the enclosing walls.

(10) The furnace 12 is supported to the ground 40 by a support construction 42 that comprises multiple vertical columns 44 supported to the ground 40 and multiple fixed horizontal beams 46 firmly attached to the vertical columns 44. The support construction 42 also comprises horizontal wall supporting beams 48 arranged parallel to the side walls 18. In addition to the inner vertical columns 44 close to the furnace 12, there are also usually, for example, outer vertical columns 44′, which are needed to provide support to other equipment of the boiler system 10, such as a steam drum, fuel bins, or particle separators (not shown in FIG. 1).

(11) The horizontal wall supporting beams 48 are arranged slidingly, by using suitable sliding surfaces 50, on two fixed horizontal beams 46 arranged parallel to the end walls 20. As can been seen from FIG. 2, there can also be cantilever beams 58 protruding towards central sections of the sidewalls 18 for providing additional support to the horizontal wall supporting beams 48. The same reference numbers are generally used for the same or corresponding elements in each of FIGS. 1 to 6.

(12) The horizontal wall supporting beams 48 are arranged close to the outwards bent intermediate wall portions 38, directly above the vertical upper portions 36 of the lower portions 32 of the side walls 18. The furnace 12 is then supported by hanging the side walls 18 of the furnace from the horizontal wall supporting beams 48 by multiple short hanger rods 52.

(13) The horizontal wall supporting beams 48 are resting on the fixed horizontal beams 46 at a level C that is vertically at a middle section of the furnace 12. When the furnace 12 heats up from ambient temperature to the operating temperature, such as 850 degrees Celsius, thermal expansion lengthens the height and width of the furnace 12. When the furnace 12 is middle-supported, as shown in FIG. 1, the middle portion of the furnace 12 remains at its original level, and the upper portion of the furnace 12, upwards from the level C, expands upwards, and the lower portion of the furnace 12, downwards from the level C, expands downwards. In addition to the vertical expansion, the furnace 12 also experiences thermal expansion in the horizontal direction. The effect and absorption of horizontal thermal expansion will be considered below.

(14) The level C is clearly below the roof of the furnace, preferably, at a level of thirty to seventy percent, even more preferably, at a level of forty to sixty percent, of the height H from the bottom of the furnace. The total height of the support construction 42 can thereby be clearly less than that of a conventional top-supported furnace 12, in which the support construction extends clearly above the roof of the furnace 12.

(15) FIG. 2 is a horizontal top view of the boiler system of FIG. 1. As is seen in FIG. 2, the end walls 20 of the furnace 12 are shorter than the side walls 18. In addition to the fixed horizontal beams 46 outside and parallel to the end walls 20, there are also inner and outer fixed horizontal beams 56, 56′ outside and parallel to the side walls 18. There are also additional inner and outer vertical columns 60, 60′ to support the inner and outer fixed horizontal beams 56, 56′ and cantilever beams 58 protruding towards the side walls 18. In practice, the furnace of a fluidized bed with more than one particle separator arranged on a side wall of the furnace 12 has a cantilever beam 58 between each pair of adjacent particle separators.

(16) FIG. 3 shows in more detail the suspension of the furnace 12 from the horizontal wall supporting beam 48. More particularly, FIG. 3 shows the sliding supporting of the horizontal wall supporting beam 48 by a sliding surface 50 in the location of a cantilever beam 58 that ends in the vicinity of the vertical upper portion 30 of the side wall 18. Supporting of the horizontal wall supporting beams 48 to the fixed horizontal beams 46 outside and parallel to the end walls 20 is generally similar to that shown in FIG. 3. The lower ends of the hanger rods 52 are attached by support lugs 60 to the edge 62 between the intermediate outwards bent wall portion 38 and vertical upper portion 36 of the lower portion 32 of the side wall 18. In order to maintain the horizontal wall supporting beams 48 at the same temperature with that of the furnace 12, they are covered by a common insulating layer 64.

(17) As seen in FIG. 3, the top ends of the hanger rods 52 are fixed to the horizontal wall supporting beam 48 by suitable fixing nuts 54, or other suitable means. Locations of the hanger rods 52 along the side walls 18, on the horizontal wall supporting beams 48 were also seen in FIG. 2 on the basis of the fixing nuts 54 above the vertical upper portion 36 of the lower portion 32 of the sidewalls 18. The cantilever beams 58 may have vertical bores to run the hanger rods 52 through the cantilever beams at the location of the beams, as was shown in FIG. 2. Alternatively, the hanger rods 52 may be omitted from the locations of the cantilever beams 58.

(18) FIG. 2 shows horizontal wall supporting beams 48 arranged on sliding surfaces 50 even on the cantilever beams 58. Alternatively, the horizontal wall supporting beams 48 could be fixed to the cantilever beams 58 at a central location of the side wall 18. It is also possible that the horizontal wall supporting beams 48 are piecewise extending, for example, from a cantilever beam 58 to a fixed horizontal beam 46 outside and parallel to an end wall 20. The parts of such a piecewise horizontal wall supporting beam are usually connected together to ensure desired longitudinal thermal movement of the piecewise wall supporting beam.

(19) FIG. 4 schematically illustrates a side view of another boiler system 10′ as seen towards a side wall 18. The boiler system 10′ corresponds otherwise to the boiler system 10 shown in FIGS. 1 and 2, but it has shorter side walls 18, whereby there is no need for additional supporting of the horizontal wall supporting beams 48 by cantilever beams at a central portion of the side walls 18. FIG. 4 particularly shows that, in order to provide a nearly uniform support to the side walls 18 of the furnace 12, the multiple hanger rods 52 are at a short distance from each other. Advantageously, the distance between adjacent hanger rods 52 is a small multiple of the distance between adjacent water tubes 22 of the water tube wall. The distance of the hanger rods is thus advantageously N times the distance between adjacent water tubes 22 of the water tube wall, where N is a small integer. Preferably, N is at most three, more preferably, at most two, and, even more preferably, N is one.

(20) According to the present invention, the horizontal wall supporting beams stay, particularly due to the thermally insulating layer 64 shown in FIG. 3, advantageously in all operating conditions at the same, or at least nearly the same, temperature as that of the furnace 12. Therefore, the thermal expansion of the horizontal wall supporting beams 48 is, in practice, identical with that of the width of the side walls 18. Due to the sliding surfaces 50, the horizontal wall supporting beams are able to slide with respect the fixed horizontal beams 46, whereby the hanger rods 52 stay during thermal expansion parallel with each other, and vertical in the direction of the plane parallel to the vertical portions of the adjacent side wall 18. In the direction of the vertical plane perpendicular to the adjacent end wall 18, the hanger rods may be uniformly tilted at a small angle that is to be taken into account in the fixing of the hanger rods to the horizontal wall supporting beams 48 and to the lugs 60.

(21) FIG. 5 schematically illustrates a side view of another embodiment of the present invention. The boiler system 10″ shown in FIG. 5 differs from that of the boiler system 10 shown in FIG. 1 mainly in that the horizontal wall supporting beams 48′ are not supported slidingly on fixed horizontal beams, but the horizontal wall supporting beams 48′ are hanging from fixed horizontal beams 46′ by main hanger rods 66. As is seen in FIG. 6, there is advantageously a single main hanger rod 66 connected to the fixed horizontal beams 46′ outside and parallel to the end walls 20. It is also possible that there are cantilever beams, similarly as shown in FIG. 2, to arrange additional main hanger rods also at central portions of the horizontal wall supporting beams 48′.

(22) The horizontal wall supporting beams 48′ are advantageously inside a common insulating layer with the furnace 12, whereby the horizontal wall supporting beams 48′ stay at the same temperature as that of the furnace 12. Differential horizontal thermal expansion between the horizontal wall supporting beams 48′ and the fixed horizontal beams 46′ is absorbed by tilting of the main hanger rods 66. In order to avoid too large tilting angles, the hanger rods have to have a sufficient length, such as at least about three meters. Longer main hanger rods absorb horizontal thermal expansion by less tilting, but they have the disadvantage of possibly increasing the height of the support construction needed for supporting the furnace at a certain height.

(23) It is to be understood that FIGS. 1 to 6 show only exemplary embodiments of the present invention, and features shown in the different embodiments can be changed to corresponding features shown in other embodiments, or to those based on general teaching of the present description, whenever it is technically possible.

(24) As becomes clear from the discussion above, different embodiments of a furnace of a boiler system with a simple and reliable supporting construction are provided. It should be understood that the elements described in connection with an embodiment also can be used in other embodiments, when possible.

(25) While the invention has been described herein by way of examples in connection with what are at present considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features and several other applications included within the scope of the invention as defined in the appended claims.